Mask compensation for matrixed-element flat-panel television display

ABSTRACT

A flat-panel television display of matrixed emitting, controlling or reflecting image elements which differ in light output per unit excitation is compensated by a mask having transmitting areas of a size and configuration corresponding to those of the image elements which vary inversely in transmissivity from area to area with the brightness of each corresponding display element.

United States Patent l 3,609,235

[72] Inventor Samuel P. Sawyer [56] References Cited E n UNITED STATESPATENTS [211 866,978 2,721,900 /1955 Oliver... 315/9 x [221 NedOct-16,1969 2,726,351 12/1955 Theile 315/9 Patented Sept. 28, 1971 [73}Assignee Zenith Radio Corporation Primary y Lake Chicago, Ill. AssistantExaminer-V. Lafranchi Atiomey.lohn J. Pederson [54] MASK COMPENSATIONFOR MATRIXED- ELEMENT FLAT-PANEL TELEVISION DISPLAY 3 Claims, 4 DrawingFigs.

[52] US. Cl l78/7.85, ABSTRACT: A flat-panel television display ofmatrixed 2 /237, 313/117 emitting, controlling or reflecting imageelements which differ [51] Int. Cl l-l04n 5/72, in light output per unitexcitation is compensated by a mask j /l lj 1/ H lk /2 havingtransmitting areas of a size and configuration cor- [50] Field of Search313/65, responding to those of the image elements which vary inverse- C,92 B, ll7;250/2l7CR,237; 178/52 A,5.2 D, ly in transmissivity from areato area with the brightness of each corresponding display element.

Ccmpen soled Display PATENTEBSEP28 I91: 3,609,235

Imaging Elements Compensated Display Inventor Samuel fzjuwyer 4, Q BMAttorney MASK COMPENSATION FOR MATRIXED-ELEMENT FLAT-PANEL TELEVISIONDISPLAY BACKGROUND OF THE INVENTION This invention generally relates toa flat-panel television display of the type having discrete matrix imageelements. More particularly, it relates to a flat-panel televisiondisplay in which such elements vary in brightness for a given excitationand are compensated so that each element will appear to be at the samebrightness level as any other, for the same excitation.

Flat-panel displays, of the type embodying matrixed arrays of discreteimage elements, such as electroluminescent cells, gas plasma cells, orinjection diodes, have in common certain deficiencies inhibiting theirwider application and use, not the least of which is a tendency of agiven constituent image element to emit or reflect more light thananother element for the same actuating signal.

Such nonuniform brightness characteristics are further aggravated by thedemands of mass production, since uniform standards for the imageelements in the vast numbers required are difficult to maintain, andimperfections in the assembly of such numbers of elements willunavoidably occur. These must be compensated if the display is not topresent a degraded image.

Therefore, it is an object of the present invention to provide animproved television flat display wherein nonuniform brightnesscharacteristics are compensated.

It is a further object of this invention to provide a televisionflat-panel display of matrixed elements wherein the light outputcharacteristics of the image elements are individually adjusted in asimple and economical manner so that light output ofeach element is thesame for the same excitation.

It is yet another object of this invention to provide a televisionflat-panel display of matrixed elements in which the light outputelements are simply and economically compensated on an individual basiswithout internal modification of the elements or panel.

A television system wherein a flat imaging panel displays televisionimage information visible from viewing locations in front of the imagingpanel is improved in accordance with the invention to include aplurality of discrete matrixed image display elements which togethercomprise the image display panel, the elements having nonuniformbrightness characteristics from element to element for a givenexcitation. Also included are means for compensating such nonuniformbrightness characteristics comprising a plurality of matrixed imagetransmitting areas of a size and configuration corresponding to those ofthe image display elements, placed between the matrixed elements and theviewing locations and in registration with the image elements, andhaving nonuniform light transmissivity from area to area. The lighttransmissivity of such transmitting areas varies inversely from elementto element with the brightness characteristics of the image elements, sothat the display has a net uniform brightness over its entire area.

BRIEF DESCRIPTION OF THE DRAWING The features of the present inventionwhich are believed to be novel are set forth with particularity in theappended claims. The invention, together with further objects andadvantages thereof, may best be understood, however, by reference to thefollowing description taken in connection with the accompanying drawing,in the several figures of which like reference numerals indicate likeelements, and in which:

FIG. I is a fragmentary front schematic view in enlarged detail of theimaging panel of a typical uncompensated flat display;

FIG. 2 is a fragmentary view in enlarged detail ofa mask for use withthe panel of FIG. 1;

FIG. 3 is a fragmentary front schematic view in enlarged detail of anembodiment of the compensated television flat display constructedaccording to the invention; and

FIG. 4 is a side view of the embodiment shown in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT The usual flat televisiondisplay panel having discrete image elements is illustrated in FIG. 1.It is the typical image display means for many well-known televisionsystems adapted to ad dress discrete display elements in, for example,the row and column fashion now common in the art. Such elements, two ofwhich are elements 10 and II, are positioned in a matrixed arrangementand fixed in an inert substrate 12, may either emit, reflect orotherwise control light, and may individually vary in light output inresponse to an actuating or excitation signal so that when the panel isviewed as a whole from viewing locations in front of the panel atelevision image can be formed and seen upon it. Typically,electroluminescent cells, gas plasma cells, liquid crystal assemblies,injection diodes, or other types of electrooptical devices may be usedas image elements, and upon being assembled into the display, willusually be found to differ in light output even when actuated by thesame excitation signal, i.e., to be of different light-producing orlight-controlling efficiency.

FIG. 2 illustrates a mask in the form of an array of light transmittingareas, typical ones of which are 20 and 21. These are positioned in amatrixed arrangement duplicating as closely as possible the arrangementof the image elements in the panel of FIG. 1, to permit these areas tobe placed in registration with corresponding image elements in thepanel. The areas of the mask are of nonuniform transmissivity, as isillustrated by elements 21 and 20, the former being comparatively clear,the latter darker. The mask transmissivity varies from area to areainversely with the degree of brightness of the image element to which itcorresponds.

Although construction of a mask meeting the foregoing requirements maybe accomplished in many ways, it is preferred to expose a photographicfilm large enough to cover the display panel to the panel while all theimage elements are uniformly actuated. The developed negativeconstitutes a film transparency which can then be used as a mask sinceit exhibits a matrix of transmitting areas of a size and configurationcorresponding to those of the image elements of the display, withtransmissivity varying so that the brighter the corresponding imageelement the darker the associated mask transmitting area. The strengthof the display excitation signal and the length of the exposure time canbe adjusted to control the degree of darkening of the film so that lightfrom the weakest image element is transmitted substantiallyundiminished. Further, if an achromatic film is used, the display to becompensated can be a color display.

This mask and the display panel is combined into the finishedcompensated television display as illustrated in FIGS. 3 and 4. The maskis positioned so that each of its transmitting areas is in registrationwith its corresponding image element and so that it is between the imageelements and the locations from which the display is to be viewed; eachsuch area then supplies only the amount of light intensity attenuationneeded to bring the element into line with the intensity of the otherelements, for a given signal, thus in effect individually adjust- ,ingeach image element. For example, originally image element 10 isrelatively brighter than element 11, as is shown in the FIG. 4 side viewand in FIG. I. But where the mask covers these elements in FIG. 3, it isseen that area 20 somewhat attentuates element 10 and is darker thanarea 21, which transmits substantially the full light output of theweaker image element II. The mask may be placed either in contact withthe display panel, as shown in FIG. 4 or as close as possible, in orderto minimize parallax distortion.

Thus the invention constitutes a compensated flat display which isadaptable to simple and rapid mass fabrication through use of economicalphotographic techniques, and enables many annoying adjustmentsordinarily necessary to obtain an acceptable flat display to bedispensed with at very little additional cost.

While particular embodiments of the invention have been shown anddescribed, it will be obvious to those skilled in the art that changesand modifications may be made without departing from the invention inits broader aspects, and, therefore, the aim in the appended claims isto cover all such changes and modifications as fall within the truespirit and scope of the invention.

lclaim:

i. in a television system wherein a flat imaging panel dis playstelevision image information visible from viewing locations in front ofsaid imaging panel, the improvement which comprises:

a plurality of discrete matrixed image display elements which togethercomprise said image display panel, said elements having nonuniformbrightness characteristics from element to element for given excitation;

and means for compensating said nonuniform brightness characteristics,comprising a mask which includes a plurality of matrixed imagetransmitting areas corresponding in size and configuration to said imagedisplay elements and is disposed between said matrixed elements and saidviewing locations and in registration with said image elements, saidmask having nonuniform light transmissivity from area to area, with thelight transmissivity of said transmitting areas varying inversely fromelement to element with the relative brightness characteristics of saidimage elements, so that the mask compensates the display to provide auniform net brightness over its entire area.

2. The improvement as in claim 1, in which said mask is in surfacecontact with said matrixed plurality of display elements.

3. The improvement as in claim I, in which said mask is a photographicfilm transparency

1. In a television system wherein a flat imaging panel displaystelevision image information visible from viewing locations in front ofsaid imaging panel, the improvement which comprises: a plurality ofdiscrete matrixed image display elements which together comprise saidimage display panel, said elements having nonuniform brightnesscharacteristics from element to element for given excitation; and meansfor compensating said nonuniform brightness characteristics, comprisinga mask which includes a plurality of matrixed image transmitting areascorresponding in size and configuration to said image display elementsand is disposed between said matrixed elements and said viewinglocations and in registration with said image elements, said mask havingnonuniform light transmissivity from area to area, with the lighttransmissivity of said transmitting areas varying inversely from elementto element with the relative brightness characteristics of said imageelements, so that the mask compensates the display to provide a uniformnet brightness over its entire area.
 2. The improvement as in claim 1,in which said mask is in surface contact with said matrixed plurality ofdisplay elements.
 3. The improvement as in claim 1, in which said maskis a photographic film transparency.